The present invention relates in general to changeable key locks and more specifically to locks having one or more keys for operating the lock between open and closed positions and wherein the internal mechanism of the lock may be selectively manipulated to accommodate the use of different keys.
Various types of key changeable locks have been developed heretofore wherein a single key is employed for turning associated internal tumbler levers of the lock between open and closed positions. An example thereof is the prior U.S. Pat. No. 1,693,731 wherein a plurality of plate like latch members are releasably secured to the bolt. A plurality of gated tumbler levers are provided on fixed pivots and are moved by the key tumblers to align the gates to the aforementioned latches. The key can be changed by releasing the latches from the bolt, placing a new key in the lock in engagement with the fixed pivot tumbler levers in latch released relation and then re-engaging the tumbler levers with the latches to fix the combination. In another prior art example, U.S. Pat. No. 1,268,900 a single changeable key lock is shown in association with a plurality of gated levers. The levers are stated as being gated at opposite ends and pivoting about a fixed axis within the lock to alternately engage primary and auxiliary, separately movable bolt and auxiliary bolt members.
The lock constructions of the prior art, including those of the references noted, do not facilitate the provision of a double changeable key lock as would be desirable for modern safety deposit locks wherein both the renter and guard keys are changeable and further are not believed to present a satisfactory construction or mode of operation for a single changeable key lock.
It is therefore the primary object of the present invention to disclose and provide a changeable key lock wherein the lock may be simply and economically constructed, assembled and manipulated in use, where the key can be easily changed and the lock is reliable and secure in its operation. It is also an object of the present invention to disclose and provide such a lock wherein two changeable keys are provided for operating the lock and the internal lock mechanism is simply and reliably manipulable for changing the combination required of both keys for opening of the lock.
Generally stated, the present invention in changeable key lock includes the provision of a plurality of gated tumbler levers and means for operating the bolt only when the tumbler levers are placed in predetermined positions of adjustment by manipulation of a selected key in the lock. Pivot means are provided on one or more of the levers for providing a plurality of individually selectable pivots about which the associated lever may pivot whereby the pivotal axis of each such lever may be varied to provide for different combinations of lever movements required to open the lock. Releasable fulcrum means are provided for engaging with the lever pivots to restrict each levers movement about a selectable one of the pivots when engaged therewith, the fulcrum means being movable when the lock is in unlocked condition to release the levers and provide for a new coding of the lever combinations prior to being re-engaged through the normal locking manipulation of the replacement keys.
More specifically, the present invention contemplates a double key changeable safety deposit lock including a movable bolt operated in assocition with a first set of renter key tumbler levers to be engaged by a renter key and a second set of guard key tumbler levers to be engaged by a guard key. Each of the foregoing levers include pivot means as aforestated for providing a plurality of individually selectable pivots whereby the pivotal axis of each lever may be varied to provide for different combinations of lever movement required by the two associated keys to align the associated gates. Releasable fulcrum means, or pivot selecting means, are also provided for normally engaging certain ones of the pivots of the two sets of levers for maintaining them in a predetermined fixed axis of pivotal movement during opening and closing operations, but allowing for a release of their pivotal axis when desired to reset the combination of levers to accommodate replacement or changed guard and/or renter keys.
A more complete understanding of the present invention, as well as a better understanding of how the present invention in key changeable lock improves upon the state of the art and achieves the objectives aforestated therefor will be provided to those skilled in the art from a consideration of the following detailed description of a preferred exemplary embodiment thereof. Reference will be made to the appended sheets of drawings which will be briefly described prior to the detailed explanation.